Skip to main content

Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

See other formats



2.  Determination of the Iron and Manganese.—The liquid from
which the-copper has been removed is treated with 2-3 drops of hydrogen
peroxide, the anode being kept immersed to dissolve the coating of man-
ganese dioxide.    The liquid is boiled for a few moments, the electrode
withdrawn and washed with water and the solution, when cold, made up
to volume in a 300 c.c. flask.    In aliquot parts the iron and manganese
are determined either volumetrically or electrolytically.

(a) VOLUMETRIC METHOD. In 50 or 100 c.c. the iron is determined by
titration with permanganate after reduction with amalgamated zinc.1 In
another aliquot part (50 or 100 c.c. according to the amount of manganese
present), the manganese is titrated by Volhard's volumetric method (see

(6) ELECTROLYTIC METHOD. In 100-200 c.c., according to the amount
of manganese present, the iron and manganese are estimated as described
for ferro-manganese.

3.  Determination of the Nickel.—In an aliquot part of the 300 c.c.
of solution (see 2), the nickel is determined by means of dimethylglyoxime
in presence of the necessary quantity of tartaric acid (see Nickel Steel).

4.  Determination of the Silicon and Lead.—The residue remaining
on the filter when the copper and manganese sulphates are taken up in
water (see i) contains all the silicon and lead of the sample as silica and
lead sulphate.    The latter is now dissolved in nitric acid containing ammo-
nium nitrate and the lead in the solution determined electrolytically in
presence of copper nitrate (see Lead-tin Alloys).

The residue insoluble in nitric acid and ammonium nitrate consists of
silica (possibly impure) and is filtered off, washed, ignited in a platinum
crucible, weighed, treated with hydrofluoric acid and again weighed; the
loss in weight represents silica (see Determination of Silicon in Iron).

With copper-manganese alloys containing little manganese (manganese
bronzes) it is advisable to determine the copper separately in two distinct por-
tions (i gram each) of the sample. When the copper is eliminated, the two
portions of manganese dioxide on the anodes are dissolved and made up together
to 300 c.c.

* *

Copper-manganese alloys contain about 25-30% of manganese with small
quantities of iron, silicon, etc. Two principal types are met with commercially :
the so-called impure alloy with 72-74% Cu, 23-24% Mn, 2-5-4-5% Fe and 0-2-
0-5% Si, and the pure alloy with 70-72% Cu, 28-30 % Mn, 0-1-0-3% Fe and 0-05-
0-1% Si.

The alloys with a low manganese content or manganese bronzes, used, owing
to strength in the hot, for valves, tie-rods for locomotives, etc., contain on the
average 4-6% Mn and such impurities as are usually met with in commercial

1 This may be prepared by dissolving 5 grams of mercury in 25 c.c. of nitric acid
(D 1-2), making the solution up to about 250 c.c., and immersing 500 grams of zinc in
granules of about i mm. diameter in it for 2-3 minutes with, continual agitation. with water, alcohol and ether, dried at 70° and weighed.es the tenacity